Endless grate stoker comprising air feed and siftings removal means



Nov. 22, 1949 E. H. SMITH ET AL 2,488,6 9

ENDLESS GRATE STOKER COMPRISING AIR FEED AND SIFTINGS REMOVAL MEANS Filed Feb. 25, 1946 2 Sheets-Sheet l /9 as K 35 24 y U f v 30 Wane/ 1949 E. H. SMITH ET AL 2,488,689

ENDLESS GRATE STOKER COMPRISING AIR FEED AND SIFTINGS REMOVAL MEANS Filed Feb. 25, 1946 2 Sheets-Sheet 2 [ma H. .SM/TH 0560/? H doH/vso/v Patented Nov. 22, 1949 UNITED STATES ENDLESS GRATE .ST OKER COMPRISING AIR 'FEED AND 'SIFTINGS REMOVAL 'MEANS Eric H. Smith and Oscar A. :Johnson, Worcester, Mass, assignors to Riley sStoker Corporation, Worcester, Mass, a cmmoration f Massachusetts Application February 25, 1946, Serial No. 649,980

This invention relates to automatic stokers, and more particularly to stokers of the endless grate type having transversely extending com-- partments through which air is supplied under forced draft to the upper run of the grate.

In the operation of such stokers there 'is a tendency for a certain amount of the finer particles of the fuel to sift through the air openings in the grate and to become depositediin the air compartments. If these deposits of siftings are allowed to accumulate to any great extent they will not only obstruct the air flow but they may become ignited and causes serious damage to the Stoker structure. Accordingly various constructions have been proposed for removing the siftings from the compartments, but in general the prior arrangements have been complicated and expensive, usually including many moving parts subject to wear or breakage. In some cases it has been impossible to remove the sittings without interrupting the operation of the stoker, or at least'shutting off the flow of air to the various compartments successively.

It is accordingly one object of the invention to provide a forced draft endless grate s'toke r having a comparatively simple and inexpensive means for removing siftings from air compartments beneath the upper run of the grate.

It is a further object of the invention to provide a stoker of the aforesaid type having a siftings removal apparatus with a minimum of movable parts and capable of operating in an eflicient and rapid manner without interfering with the normal operation of the stoker.

With these and other objects in View, as will be apparent to those skilled in the art, the invention resides in the combination :or parts set forth in the specification and covered by the claims appended hereto.

Referring to the drawings illustrating one embodiment of the invention, and. in which like reference numerals indicate like parts,

Fig. 1 is a longitudinal section throughan-endless grate forced draft stoker, the section being taken on the 'line l-l of FigfiZ;

Fig. 2 "is a plan view taken'in section on :the line 22'of'Fig, 1.;

Fig. 73 is a section taken on the line 3i3 M Fig. 2;

Fig. 4 is a section taken on the line 4-4 of Fig. '1, at .a somewhat larger scale; and

Fig. 5 is a fragmentary section taken on't'he line 5-5 of Fig. 4, atalconsiderably largerscale.

Theaem'bodiment illustrated comprises walls 'illl forming a furnace cr -combustionchamber which is fired by an automatic stoker having an endless grate "H supplied with fuel from a hopper 12 (Fig. 1) at the front of the furnace. The zgrate may be of any suitable and well-known construction, and as indicated in Fig. 4 it may include 4 Claims. (Cl. 510-40) a plurality of longitudinally extending :endless chains 14, the upper run of each chain being carried by a track I5, the tracks being supported by transverse horizontal beams l6. These beams are preferably of aflanged cross section, such as I-beams, and their lower flanges support horizontal plates Hi. This construction provides :a plurality of transversely extending separate lair compartments l9 beneath the upper run of the grate M, the plates I8 forming the bottomwails of the compartments. Each compartment communicates at one end with a separate air box 21 having an access door 22 in its .outer wall. Air under pressure is supplied to each box :21 by means of a separate :duct 23 provided "with a damper 24. As so far described the 'stoker construction is well-known in the art.

During the operation of the sto'ker some thefiner particles of fuel will drop throughthe grate into the air compartments, and the invention lprovides means for collecting and removing such 'siftings. For this purpose a transversesubstantially horizontal pipe '26 is mounted within each compartment I9 and extends along i-the a central portion of the bottom plate '18. These pipes :are preferably of square or other rectangular cross section, and they are provided "with openings '2'! in their upper walls to receive (the sittings. The inner ends of the pipes are'prefe'rably open to the atmosphere, and their outer ends are connected by branch pipes 28 to iaimain header 30 leading to a suitable suction-producing device, such as an ejector, fan, .or'the like (not shown). Each branch pipe 28 is provided with a slide valve 3|. The entrance openings 2:! in the pipes 26 are controlled by :slide plates 33 which rest on the tops of the pipes' 'a'nd have openings 34 arranged to register with ithepip'e openings 2'! when the plates are moved outwardly. As' illustrated, each pipeZB supports two o'f'th'e slide plates 33, each plate having an operating rod "35 which extends outwardly and "upwardly through the outer wall of the corresponding air box 2]. Lugs 3'6 (Fig. 4) project upward-1y from the plates 33.

The invention provides means to direct the accumulating siftings toward-the pipe openings '21. The preferred construction for this purposecomprises a pair of plates 38 extending lengthwise of each air compartment is in 'a downwardly converging or V-shaped arrangement. The upper edges of these plates are secured to flanges "39 which project laterally from the beams "l6, and thelower portions of the plates are connected *by brackets 48 (Fig. 5) to the pipe 2-6. 'The-lower edges of the plates are slightly spaced apart to provide a slot in registration with the openings 21,an'd"they are located closely above the slide plates 33. Each plate '38 is provided withopenines 42 near its upper edge to permit flow of combustion air upwardly therethrough, these openings preferably being located beneath the grate tracks as shown in Fig. 4. It will be clear from Fig, 4 that the space between each pair of plates 38 is fully open at one end for the direct reception of air entering the corresponding air compartment l9, so that part of the air will flow above the plates while part will flow beneath the plates and thence upwardly through the openings 42. Thus the entire cross-sectional area of the air compartment is available for air flow, and the air will be distributed very uniformly across the stoker.

The operation of the invention will now be apparent from the above disclosure. The grate H will be supplied with fuel from the hopper l2, and combustion will take place as the fuel bed moves slowly to the rear. Air for combustion will enter the compartments 5!] from the ducts 23 and the air boxes 2|, under the control of the dampers 24. Some of the air will enter beneath the plates 38 and flow upwardly through the openings 42. Fine fuel which sifts through the grate will collect in the V-shaped trough or hopper formed by the plates 38. The tracks [5 will shield the openings 42 from the falling siftings. The valves 3| are normally closed, and the openings 21 are normally closed by the slide plates 33. When the operator wishes to clean out the siftings from a particular compartment, he will open the corresponding valve 3| and pull one of the slide plates 33 outwardly by means of its rod 35, thus uncovering the openings 21. During this movement of the slide plate the lugs 36 will break up any arches which may have formed in the siftings. The siftings will now enter the openings 21 under the combined effect of gravity, the air pressure within the compartment, and the suction within the pipe 26. A strong current of air will enter the open end of the pipe 26 and carry the siftings along the pipe, and through the corresponding branch pipe 28 and the pipe 30 to a suitable place of disposal. Preferably they are eventually returned by some means to the furnace for combustion therein. Only a very brief time will be required to discharge the siftings above one slide plate 33, whereupon this plate will be closed and the other slide plate in the same compartment will be opened for the necessary interval. As soon as the cleaning of a compartment is completed, the corresponding valve 3| will be closed, and another compartment may-be cleaned in the same manner. The removal of siftings is accomplished expeditiously and without in the least interfering with the normal operation of the stoker. The construction is simple and inexpensive, and free from moving parts subject to wear and breakage.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. An automatic stoker comprising an endless grate having an upper run to support a fuel bed, transverse beams dividing the space beneath the upper run of the grate into a plurality of separate air compartments, plates extending between the beams to form the bottom walls of the compartments, a transversely extending pipe within each compartment and adjacent the bottom wall thereof, the pipes having openings in their upper walls for the admission of fine fuel siftings, a pair of downwardly converging plates within each compartment to direct the siftings toward the pipe, means to supply air to one end of each compartment, the said converging plates having openings in their upper portions for the upward .flow of air therethrough and the space between each air of converging plates being open at one end for the direct reception of air entering the corresponding air compartment, a suction header, and branch pipes connecting one end of each pipe to the header.

2. An automatic stoker comprising an endless grate having an upper run to support a fuel bed, transverse beams dividing the space beneath the upper run of the grate into a plurality of separate air compartments, plates extending between the beams to form the bottom walls of the compartments, a transversely extending pipe within each compartment and adjacent the bottom wall thereof, the pipes being of rectangular cross section with flat upper walls provided with openings therein for the admission of fine fuel siftings, valve plates resting on the said upper walls and slidable longitudinally of the pipes to control the openings, a pair of downwardly converging plates within each compartment to direct the siftings toward the pipe, a suction header, and branch pipes connecting one end of each pipe to the header.

3. An automatic stoker comprising an endless grate having an upper run to support a fuel bed, transverse beams dividing the space beneath the upper run of the grate into a plurality of separate air compartments, plates extending between the beams to form the bottom walls of the compartments, a separate air box at the outer end of each compartment to supply air thereto, a transversely extending pipe within each compartment and adjacent the bottom wall thereof, the pipes being of rectangular cross section with flat upper walls provided with openings therein for the admission of fine fuel sittings, valve plates resting on the said upper walls, rods extending outwardly from the valve plates and through the air boxes to slide the valve plates along the pipes and thus control the openings, a pair of downwardly converging plates within each compartment to direct the siftings toward the pipe, a suction header, and branch pipes connecting one end of each pipe to the header.

4. An automatic stoker as covered by claim 1 in which spaced longitudinally extending tracks are provided to support the upper run of the grate, and the air openings in the converging plates are located beneath the said tracks.

ERIC H. SMITH. OSCAR A. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 835,409 Dillon Nov. 9, 1906 851,054 Bassler Apr. 23, 1907 1,672,563 Fox June 5, 1928 1,698,113 Van Brunt Jan. 8, 1929 1,707,893 Bennis Apr. 2, 1929 1,887,153 Grohn Nov. 8, 1932 1,943,780 Allen Jan. 16, 1934 1,961,552 Cruikshank June 5, 1934 FOREIGN PATENTS Number Country Date 309,843 Great Britain Apr. 9, 1929 

